will the 2+ cation concentr A student dispenses a 10.00 mL portion of Bay water
ID: 997725 • Letter: W
Question
will the 2+ cation concentr A student dispenses a 10.00 mL portion of Bay water into a beaker, then pours the Bay water from the beaker into an Erlenmeyer flask for the EDTA titration. Will the 2+ cation concentration that this student calculates be higher than, lower than, or equal to the actual concentration (assuming that the rest of the procedure was done correctly)? If the student recognizes what he did before starting the titration, can the student correct the error (without getting a fresh Bay water sample)? If so, how? 3. A student puts his EDTA solution into a wet beaker before pouring it into the buret. Will the 2+ cation concentration that this student calculates be higher than, lower than, or equal to the actual concentration (assuming that the rest of the procedure was done correctly)? If the student recognizes what he did before starting the titration, can the student correct the error (without getting a fresh Bay water sample)? If so, how?Explanation / Answer
2. If the student transferred the original solution from beaker to erlenmeyer flask,
a. Some of the water would be left adhered to the beaker and would not be transferred to the flask. This thus would give an error in measurement. The calculated value thus would be higher than the actual value for the +2 cation in the bay water sample.
b. If the student has done the titration belore. To correct the reading one may titrant the leftover liquid in the beaker with EDTA and then add the two volumes used to calculate the final concentration of the +2 cation in the sample.
3. If the student puts EDTA sample in wet beaker, before pouring the buret,
a. The overall concentration of EDTA would be lower due to dilution with the water present in the beaker. A higher amount (volume) of EDTA would be used for titration. Thus, the concentration calculated for +2 cation would be higher than the actual value.
b. If the student had done the titration before. One may correct this error by standardizing the EDTA sample separately and then recalculating the concentration of +2 cation in the bay water sample.
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